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Copper is a chemical element with the symbol Cu (from Latin: cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orange color. Copper is used as a conductor of heat and electricity, as a building material, and as a constituent of various metal alloys, such as sterling silver used in jewelry, cupronickel used to make marine hardware and coins, and constantan used in strain gauges and thermocouples for temperature measurement.

Quick facts: Copper, Appearance, Standard atomic
Copper, 29Cu
Appearancered-orange metallic luster
Standard atomic weight Ar°(Cu)
  • 63.546±0.003
  • 63.546±0.003 (abridged)[1]
Copper in the periodic table


Atomic number (Z)29
Groupgroup 11
Periodperiod 4
Block  d-block
Electron configuration[Ar] 3d10 4s1
Electrons per shell2, 8, 18, 1
Physical properties
Phase at STPsolid
Melting point1357.77 K (1084.62 °C, 1984.32 °F)
Boiling point2835 K (2562 °C, 4643 °F)
Density (near r.t.)8.96 g/cm3
when liquid (at m.p.)8.02 g/cm3
Heat of fusion13.26 kJ/mol
Heat of vaporization300.4 kJ/mol
Molar heat capacity24.440 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1509 1661 1850 2089 2404 2834
Atomic properties
Oxidation states−2, 0,[2] +1, +2, +3, +4 (a mildly basic oxide)
ElectronegativityPauling scale: 1.90
Ionization energies
  • 1st: 745.5 kJ/mol
  • 2nd: 1957.9 kJ/mol
  • 3rd: 3555 kJ/mol
  • (more)
Atomic radiusempirical: 128 pm
Covalent radius132±4 pm
Van der Waals radius140 pm
Spectral lines of copper
Other properties
Natural occurrenceprimordial
Crystal structure face-centered cubic (fcc)
Speed of sound thin rod(annealed)
3810 m/s (at r.t.)
Thermal expansion16.5 µm/(m⋅K) (at 25 °C)
Thermal conductivity401 W/(m⋅K)
Electrical resistivity16.78 nΩ⋅m (at 20 °C)
Magnetic orderingdiamagnetic[3]
Molar magnetic susceptibility−5.46×10−6 cm3/mol[4]
Young's modulus110–128 GPa
Shear modulus48 GPa
Bulk modulus140 GPa
Poisson ratio0.34
Mohs hardness3.0
Vickers hardness343–369 MPa
Brinell hardness235–878 MPa
CAS Number7440-50-8
Namingafter Cyprus, principal mining place in Roman era (Cyprium)
DiscoveryMiddle East (9000 BC)
Symbol"Cu": from Latin cuprum
Main isotopes of copper
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
63Cu 69.15% stable
64Cu syn 12.70 h ε 64Ni
β 64Zn
65Cu 30.85% stable
67Cu syn 61.83 h β 67Zn
 Category: Copper
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Copper is one of the few metals that can occur in nature in a directly usable metallic form (native metals). This led to very early human use in several regions, from circa 8000 BC. Thousands of years later, it was the first metal to be smelted from sulfide ores, circa 5000 BC; the first metal to be cast into a shape in a mold, c. 4000 BC; and the first metal to be purposely alloyed with another metal, tin, to create bronze, c. 3500 BC.[5]

In the Roman era, copper was mined principally on Cyprus, the origin of the name of the metal, from aes cyprium (metal of Cyprus), later corrupted to cuprum (Latin). Coper (Old English) and copper were derived from this, the later spelling first used around 1530.[6]

Commonly encountered compounds are copper(II) salts, which often impart blue or green colors to such minerals as azurite, malachite, and turquoise, and have been used widely and historically as pigments.

Copper used in buildings, usually for roofing, oxidizes to form a green verdigris (or patina). Copper is sometimes used in decorative art, both in its elemental metal form and in compounds as pigments. Copper compounds are used as bacteriostatic agents, fungicides, and wood preservatives.

Copper is essential to all living organisms as a trace dietary mineral because it is a key constituent of the respiratory enzyme complex cytochrome c oxidase. In molluscs and crustaceans, copper is a constituent of the blood pigment hemocyanin, replaced by the iron-complexed hemoglobin in fish and other vertebrates. In humans, copper is found mainly in the liver, muscle, and bone.[7] The adult body contains between 1.4 and 2.1 mg of copper per kilogram of body weight.[8]

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